As it is well known, the demand for switches having high performances in terms of insulation and insertion loss has pushed the search for new technological and design approaches. In particular, MEMS (Micro Electro-Mechanical System) switches dissipate little power thus obtaining a considerable energy consumption savings. Further, MEMS switches have a high linearity on the whole frequency band, avoiding signal distortion phenomena, and they have a high Insertion Loss, i.e. a low signal attenuation. Moreover, these devices can be manufactured on silicon substrates thus offering an integration possibility with other electronic components integrated in a traditional way or in more complex systems.
A first known technical approach to manufacture a switch operated in an electrostatic way and manufactured with a micromachining technique is described in U.S. Pat. No. 5,638,946. This switch 1, as shown in FIG. 1, is manufactured by using a dielectric connection bridge P insulating the overhanging bar SS and leading the electrical contact. Although advantageous in several aspects, this first approach has several drawbacks. Because of the high number of cycles to be supported by the hanging bar, made of a metal or dielectric material, this approach is thus not very reliable.
A second approach provides instead the use of a switch operated in an electrostatic way, manufactured via a surface micromachining technique involving the use of two wafers for manufacturing the metal contact. One wafer is dedicated to manufacturing the balancing structure and the other wafer to manufacturing transmission lines. The removal of the wafer allowing the mobile structure to be manufactured is required to release the switch movement for which this wafer does not serve as part of the integrated package. The distance between the balancing mobile structure and the contact electrode is given by gold spacers. This approach also has some drawbacks. Gold spacers have the disadvantage of having a variable thickness with the pressure needed to assemble the two wafers for which high operating voltage variations occur.
In a third known approach, a switch, as shown in FIG. 2, manufactured on a gallium arsenide substrate AG, operated in an electrostatic way, comprises a silicon bar S covered with aluminum and with a platinum-on-gold metal contact C. The disadvantage of this structure is the use of a metal like platinum for the contact having a relatively high resistivity with respect to gold or copper (less than 2 mWcm).
FIG. 3 shows a magnetically operated switch IM, comprising a bar S1 whereon a magnet M and known starting electrodes A are located. The disadvantage is that the required structures for creating the magnetic field weigh down the overall switch structure. Moreover some interference could arise with the radio frequency signal passing through the contact C1.
A further approach provides the manufacture of a switch operated in an electrostatic way manufactured by using two hanging bars, manufactured during the same process step, and arched upwards with respect to the supporting substrate plane. One hanging bar serves as a contact and the other serves for the contact latch. By operating the second bar the contact is locked as between the gears of watch rollers. The disadvantage is due to the bending and relative height of the two bars that highly depend on the technological process conditions.